Zoom lens system

ABSTRACT

Object is to provide an inner-focusing type zoom lens system carrying out focusing by moving a portion of a first lens group suitable for an auto-focus SLR camera. A zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first and the second lens groups increases, and a distance between the second and the third lens groups decreases. The first lens group is composed of, in order from the object, a  1 A lens group G 1 A having positive refractive power, and a  1 B lens group G 1 B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the  1 B lens group G 1 B to the object.

The disclosure of the following priority applications are herein incorporated by reference:

Japanese Patent Application No. 2004-099773 filed on Mar. 30, 2004,

Japanese Patent Application No. 2004-105319 filed on Mar. 31, 2004,

Japanese Patent Application No. 2005-036624 filed on Feb. 14, 2005 and

Japanese Patent Application No. 2005-036633 filed on Feb. 14, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system suitable for a single-lens-reflex (SLR) camera using a silver-halide film or a solid-state imaging device and in particular to an internal-focusing zoom lens system capable of focusing by moving a portion of the optical system in a first lens group and also in particular to a compact zoom lens system having a vibration reduction function with a zoom ratio of about four and an angle of view of about 22° or more in a wide-angle end state.

2. Related Background Art

As a conventional focusing method for a zoom lens, a front-lens-group focusing carrying out by moving the most object side lens group to the object has been generally known. This method has a merit that the moving amount for focusing is determined in accordance with the object distance regardless of the zooming position, so that it is effective for simplifying the focusing mechanism. This method makes it possible to construct a first lens group with about three lens elements, so that it is effective for simplifying the construction of the lens system and lowering the manufacturing cost. However, since the moving lens group for focusing is exposed outside, when unexpected force is applied to the lens system, the focusing mechanism, in particular an auto-focusing mechanism, may be damaged. On the other hand, zoom lens systems with an internal focusing method, in which focusing is carried out by a lens group other than the first lens group, have been proposed in large numbers. However, it also has a problem that the moving amount for focusing largely varies in accordance with the zoom position.

In order to solve the problems, a focusing method, in which the first lens group is composed of a front lens group having positive refractive power and a rear lens group having positive refractive power and focusing is carried out by moving the rear lens group to the object, has been proposed in Japanese Patent Application Laid-Open Nos. 6-51202, 2000-19398, and 2000-284174.

However, although each example disclosed by Japanese Patent Application Laid-Open No. 6-51202 constructing the first lens group by three lens elements as a whole, two lens elements in the front lens group and one lens element in the rear lens group, is suitable for simplifying the construction and lowering the manufacturing cost, since focusing is carried out by moving only a single lens element with positive refractive power, spherical aberration, on-axis chromatic aberration and lateral chromatic aberration becomes large upon focusing a close-range object, so that it is undesirable for obtaining high optical performance.

Moreover, each example disclosed by Japanese Patent Application Laid-Open No. 2000-19398 requires five lens elements in the first lens group, three lens elements in the front lens group and two lens elements in the rear lens group, so that it is not suitable for simplifying the construction or lowering the manufacturing cost.

Furthermore, each example disclosed by Japanese Patent Application Laid-Open No. 2000-284174 requires four lens elements in the first lens group, one lens element in the front lens group and three lens elements in the rear lens group, so that it is not suitable for simplifying the construction or lowering the manufacturing cost.

Moreover, telephoto zoom lenses with a vibration reduction mechanism having a zoom ratio of about four have been proposed in Japanese Patent Application Laid-Open Nos. 8-62541 and 10-133114.

Examples disclosed in Japanese Patent Application Laid-Open No. 8-62541 are a five-group zoom lens with positive-negative-positeve-positeve-negative power arrangement or a six-group zoom lens with positive-negative-positive-negative-positive-negative power arrangement moving the second lens group having negative refractive power for vibration reduction. However, in these disclosures, since the effective diameter of the second lens group is 25 mm or more, the vibration reduction mechanism becomes large, so that it becomes difficult to make the zoom lens system be compact.

Examples disclosed in Japanese Patent Application Laid-Open No. 10-133114 are a five-group zoom lens with positive-negative-negateve-positeve-negative power arrangement moving a portion of lens group in the fourth lens group having positive refractive power for vibration reduction. However, in these disclosures, since the effective diameter of the vibration reduction lens group in the fourth lens group is 25 mm or more, the vibration reduction mechanism becomes large, so that it becomes difficult to make the zoom lens system be compact.

SUMMARY OF THE INVENTION

The present invention is made in view of the aforementioned problems and has an object to provide an internal focusing zoom lens system suitable for an auto focus SLR camera using a silver-halide film or a solid-state imaging device, carrying out focusing by moving a portion of a first lens group, having a zoom ratio of about four and an angle of view of 22° or more in the wide-angle end state, and suitable for simplifying the lens construction of the first lens group and lowering manufacturing cost without compromising compactness or high optical performance.

According to one aspect of the present invention, a zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object, and the following conditional expressions (1) through (4) are satisfied: 1.55<f1/fw<2.20  (1) −0.55<f2/fw<−0.30  (2) 2.0<f1A/f1B<4.0  (3) 0.16<DAB/fw<0.30  (4) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused on infinity.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group preferably move to the object.

In one preferred embodiment of the present invention, the zoom lens system further includes a fourth lens group having negative refractive power to an image side of the third lens group. When the state of lens group positions varies from the wide-angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group varies, and the following conditional expressions (5) through (7) are preferably satisfied: 0.35<f3/fw<0.70  (5) −1.50<f4/fw <−0.70  (6) −0.10<(D34w−D34t)/fw<0.10  (7) where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.

In one preferred embodiment of the present invention, the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions (8) and (9) are preferably satisfied: 50<ν1A  (8) 35<ν1BP−ν1BN  (9) where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.

In one preferred embodiment of the present invention, the negative meniscus lens and the positive lens in the 1B lens group are preferably cemented with each other.

According to another aspect of the present invention, a zoom lens system with a vibration reduction mechanism includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group varies. The fourth lens group is composed of, in order from the object, a 41 lens group, a 42 lens group having negative refractive power, and a 43 lens group. At least one of the 41 lens group and the 43 lens group has positive refractive power. Image blur on an image plane caused by a camera shake is reduced by moving only the 42 lens group perpendicular to the optical axis.

In one preferred embodiment of the present invention, the following conditional expression (10) is preferably satisfied: 0.10<f42/f4<0.90  (10) where f4 denotes the focal length of the fourth lens group, and f42 denotes the focal length of the 42 lens group.

In one preferred embodiment of the present invention, the following conditional expressions (11) and (12) are preferably satisfied: −2.10<f4/fw<−0.70  (11) −2.10<(1/f41+1/f43)·f4<−0.40  (12) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f41 denotes the focal length of the 41 lens group and f43 denotes the focal length of the 43 lens group.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fourth lens group preferably move to the object.

In one preferred embodiment of the present invention, the 41 lens group preferably includes at least one positive lens, the 42 lens group preferably includes at least one positive lens and at least one negative lens, and the 43 lens group preferably includes at least one positive lens.

In one preferred embodiment of the present invention, the 41 lens group includes, in order from the object, a negative lens having a concave surface facing to the image, and a positive lens having a convex surface facing to the object, and the following conditional expression (13) is preferably satisfied: 0.20<n41N−n41P  (13) where n41N denotes refractive index of the negative lens in the 41 lens group at d-line (λ=587.6 nm), and n41P denotes refractive index of the positive lens in the 41 lens group at d-line.

In one preferred embodiment of the present invention, the 42 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (14) is preferably satisfied: 10.0<ν42N−ν42P  (14) where ν42N denotes Abbe number of the double concave negative lens in the 42 lens group at d-line (λ=587.6 nm), and ν42P denotes Abbe dumber of the positive lens in the 42 lens group at d-line.

In one preferred embodiment of the present invention, the zoom lens system preferably consists only of, in order from the object, the first lens group, the second lens group, the third lens group, and the fourth lens group.

In one preferred embodiment of the present invention, a fifth lens group having positive refractive power is preferably arranged to the image side of the fourth lens group.

In one preferred embodiment of the present invention, focusing from infinity to a close-range object is preferably carried out by moving the first lens group as a whole to the object.

In one preferred embodiment of the present invention, focusing from infinity to a close-range object is carried out by moving the second lens group as a whole to the object, and the following conditional expression (15) is preferably satisfied: −0.98<M2t<−0.80  (15) where M2t denotes the magnification of the second lens group in the telephoto end state.

In one preferred embodiment of the present invention, the first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power, and focusing from infinity to a close-range object is preferably carried out by moving only the 1B lens group to the object.

According to another aspect of the present invention, a zoom lens system with a vibration reduction mechanism includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The third lens group is composed of, in order from the object, a 31 lens group having positive refractive power, a 32 lens group having negative refractive power, and a 33 lens group. Image blur on an image plane caused by a camera shake is reduced by moving only the 32 lens group perpendicular to the optical axis.

In one preferred embodiment of the present invention, the following conditional expressions (16) through (20) are preferably satisfied: 1.40<f1/fw<2.00  (16) −0.53<f2/fw<−0.32  (17) 0.35<f3/fw<0.65  (18) −2.00<f32/f3<−0.80  (19) −0.20<f3/f33<0.50  (20) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f3 denotes the focal length of the third lens group, f32 denotes the focal length of the 32 lens group, and f33 denotes the focal length of the 33 lens group.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group preferably move to the object.

In one preferred embodiment of the present invention, the 31 lens group preferably includes at least three positive lenses and at least one negative lens, the 32 lens group preferably includes at least one positive lens and at least one negative lens, and the 33 lens group preferably includes at least one positive lens and at least one negative lens.

In one preferred embodiment of the present invention, the 31 lens group includes, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative lens having a concave surface facing to the object, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens, and the following conditional expressions (21) and (22) are preferably satisfied: 0.20<n31N−n31P  (21) 30.0<ν31P−ν31N  (22) where n31N denotes refractive index of the negative lens in the first cemented lens at d-line (λ=587.6 nm), n31P denotes refractive index of the positive lens in the first cemented lens at d-line, ν31N denotes Abbe number of the negative lens in the first cemented lens at d-line, and ν31P denotes Abbe number of the positive lens in the first cemented lens at d-line.

In one preferred embodiment of the present invention, the 32 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (23) is preferably satisfied: 10.0<ν32N−ν32P  (23) where ν32N denotes Abbe number of the double concave negative lens in the 32 lens group at d-line (λ=587.6 nm), and ν32P denotes Abbe number of the positive lens in the 32 lens group at d-line.

In one preferred embodiment of the present invention, the 32 lens group is composed of, in order from the object, a cemented lens constructed by a positive lens having a convex surface facing to the image cemented with a double concave negative lens, and the following conditional expression (24) is preferably satisfied: −2.00<(r32R+r32F)/(r32R−r32F)<−0.70  (24) where r32F denotes the radius of curvature of the object side surface of the positive lens in the 32 lens group, r32R denotes the radius of curvature of the image side surface of the double concave negative lens in the 32 lens group.

In one preferred embodiment of the present invention, the following conditional expression (25) is preferably satisfied: 0.40<r32S/f32<0.90  (25) where r32S denotes the radius of curvature of the cemented lens in the 32 lens group, and f32 denotes the focal length of the 32 lens group.

In one preferred embodiment of the present invention, the zoom lens system preferably consists only of, in order from the object, the first lens group, the second lens group, and the third lens group.

In one preferred embodiment of the present invention, the first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power, focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object, and the following conditional expression (26) is preferably satisfied: 1.70<f1A/f1B<4.00  (26) where f1A denotes the focal length of the 1A lens group and f1B denotes the focal length of the 1B lens group.

Other features and advantages according to the present invention will be readily understood from the detailed description of the preferred embodiments in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a sectional view of a zoom lens system according to Example 1 of a first embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 2A and 2B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.

FIGS. 3A and 3B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.

FIGS. 4A and 4B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

FIG. 5 is a diagram showing a sectional view of a zoom lens system according to Example 2 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 6A and 6B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.

FIGS. 7A and 7B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.

FIGS. 8A and 8B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

FIG. 9 is a diagram showing a sectional view of a zoom lens system according to Example 3 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 10A and 10B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.

FIGS. 11A and 11B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.

FIGS. 12A and 12B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

FIG. 13 is a diagram showing a sectional view of a zoom lens system according to Example 4 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 14A and 14B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.

FIGS. 15A and 15B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.

FIGS. 16A and 16B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

FIG. 17 is a diagram showing a sectional view of a zoom lens system according to Example 5 of a second embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 18A and 18B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 19 shows various aberrations of the zoom lens system according to Example 5 of the second embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 20A and 20B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 21 is a diagram showing a sectional view of a zoom lens system according to Example 6 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 22A and 22B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 23 shows various aberrations of the zoom lens system according to Example 6 of the second embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 24A and 24B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 25 is a diagram showing a sectional view of a zoom lens system according to Example 7 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 26A and 26B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 27 shows various aberrations of the zoom lens system according to Example 7 of the second embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 28A and 28B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 29 is a diagram showing a sectional view of a zoom lens system according to Example 8 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 30A and 30B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 31 shows various aberrations of the zoom lens system according to Example 8 of the second embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 32A and 32B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 33 is a diagram showing a sectional view of a zoom lens system according to Example 9 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 34A and 34B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 35 shows various aberrations of the zoom lens system according to Example 9 of the second embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 36A and 36B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 37 is a diagram showing a sectional view of a zoom lens system according to Example 10 of a third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 38A and 38B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 39 shows various aberrations of the zoom lens system according to Example 10 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 40A and 40B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 41 is a diagram showing a sectional view of a zoom lens system according to Example 11 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 42A and 42B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 43 shows various aberrations of the zoom lens system according to Example 11 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 44A and 44B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 45 is a diagram showing a sectional view of a zoom lens system according to Example 12 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 46A and 46B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 47 shows various aberrations of the zoom lens system according to Example 12 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 48A and 48B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 49 is a diagram showing a sectional view of a zoom lens system according to Example 13 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 50A and 50B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 51 shows various aberrations of the zoom lens system according to Example 13 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 52A and 52B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 53 is a diagram showing a sectional view of a zoom lens system according to Example 14 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 54A and 54B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 55 shows various aberrations of the zoom lens system according to Example 14 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 56A and 56B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 57 is a diagram showing a sectional view of a zoom lens system according to Example 15 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 58A and 58B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 59 shows various aberrations of the zoom lens system according to Example 15 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 60A and 60B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

FIG. 61 is a diagram showing a sectional view of a zoom lens system according to Example 16 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

FIGS. 62A and 62B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.

FIG. 63 shows various aberrations of the zoom lens system according to Example 16 of the third embodiment in an intermediate focal length state upon focusing at infinity.

FIGS. 64A and 64B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[First Embodiment]

The zoom lens system according to the first embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases.

The first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-rang object is carried out by moving only the 1B lens group G1B to the object.

With this construction, it can be prevented to expose movable lens group for focusing, so that it is advantageous for auto focus. Moreover, by composing the first lens group of the 1A lens group G1A having positive refractive power and the 1B lens group G1B having positive refractive power, increase in the number of lens elements can be prevented and variation in aberration upon focusing can be suppressed.

The zoom lens system according to the first embodiment of the present invention satisfies the following conditional expressions (1) through (4): 1.55<f1/fw<2.20  (1) −0.55<f2/fw<−0.30  (2) 2.0<f1A/f1B<4.0  (3) 0.16<DAB/fw<0.30  (4) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused on infinity.

Conditional expression (1) defines an appropriate range of the focal length of the first lens group. When the ratio f1/fw is equal to or falls below the lower limit of conditional expression (1), positive refractive power of the first lens group becomes large, so that it becomes difficult to satisfactorily correct aberrations with fewer number of lens elements. On the other hand, when the ratio f1/fw is equal to or exceeds the upper limit of conditional expression (1), the total length of the zoom lens system becomes large, so that it is undesirable.

In order to secure the effect of the present invention, it is preferable that the lower limit of conditional expression (1) is set to 1.60 and the upper limit to 2.00.

Conditional expression (2) defines an appropriate range of the focal length of the second lens group. When the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (2), negative refractive power of the second lens group becomes large, so that it becomes difficult to correct various aberrations. On the other hand, when the ratio f2/fw is equal to or falls below the lower limit of conditional expression (2), the total length of the zoom lens system becomes large, so that it is undesirable.

In order to fully secure the effect of the present invention, it is preferable that the lower limit of conditional expression (2) is set to −0.50 and the upper limit to −0.35.

Conditional expression (3) defines an appropriate range of the ratio of the focal length of the 1A lens group to that of the 1B lens group. When the ratio f1A/f1B is equal to or exceeds the upper limit of conditional expression (3), positive refractive power of the 1B lens group becomes strong, so that it takes larger number of lens elements in the 1B lens group to correct aberrations. On the other hand, when the ratio f1A/f1B is equal to or falls below the lower limit of conditional expression (3), positive refractive power of the 1A lens group becomes strong, so that it takes larger number of lens elements in the 1A lens group to correct aberrations.

In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (3) is set to 2.20 and the upper limit to 3.85.

Conditional expression (4) defines an appropriate range of the distance between the 1A lens group G1A and the 1B lens group G1B. When the ratio DAB/fw is equal to or exceeds the upper limit of conditional expression (4), the diameter of the 1A lens group becomes large, so that it is undesirable. On the other hand, when the ratio DAB/fw is equal to or falls below the lower limit of conditional expression (4), the air space for moving the 1B lens group upon focusing becomes narrow, so that it becomes difficult to secure the closest shooting distance to be sufficiently near.

In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (4) is set to 0.18 and the upper limit to 0.25.

It is preferable that when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group move to the object. In this construction, the total lens length of the zoom lens system in the wide-angle end state can be compact.

Moreover, it may be possible to construct the zoom lens system by including a fourth lens group having negative refractive power to the image side of the third lens group and varying the distance between the third lens group and the fourth lens group upon zooming from the wide-angle end state to the telephoto end state. By arranging the fourth lens group having negative refractive power to the image side of the third lens group, the zoom lens system becomes a telephoto type power arrangement, so that it is effective to shorten the total lens length of the zoom lens system. Moreover, by varying the distance between the third lens group and the fourth lens group, variation in astigmatism and curvature of field can be suppressed.

In the zoom lens system according to the first embodiment of the present invention, it is preferable to satisfy the following conditional expressions (5) through (7): 0.35<f3/fw<0.70  (5) −1.50<f4/fw<−0.70  (6) −0.10<(D34w−D34t)/fw<0.10  (7) where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.

Conditional expression (5) defines an appropriate range of the focal length of the third lens group. When the ratio f3/fw is equal to or falls below the lower limit of conditional expression (5), positive refractive power of the third lens group becomes strong, so that it becomes difficult to correct various aberrations as well as spherical aberration. On the other hand, when the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (5), the total length of the zoom lens system becomes large, so that it is undesirable.

In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (5) is set to 0.40 and the upper limit to 0.60.

Conditional expression (6) defines an appropriate range of the focal length of the fourth lens group. When the ratio f4/fw is equal to or exceeds the upper limit of conditional expression (6), negative refractive power of the fourth lens group becomes strong, so that it becomes difficult to correct coma and distortion. On the other hand, when the ratio f4/fw is equal to or falls below the lower limit of conditional expression (6), negative refractive power of the fourth lens group becomes weak decreasing the effect of the telephoto type power arrangement, so that it becomes difficult to make the total lens length be compact.

In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (6) is set to −1.20 and the upper limit to −0.85.

Conditional expression (7) defines an appropriate range of difference between the distance from the third lens group to the fourth lens group in the wide-angle end state and that in the telephoto end state. When the ratio (D34w−D34t)/fw is equal to or falls below the lower limit of conditional expression (7), or is equal to or exceeds the upper limit of conditional expression (7), it becomes difficult to satisfactorily correct variation in astigmatism and curvature of field upon zooming.

In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (7) is set to −0.05 and the upper limit to 0.05.

In order to suppress the number of lens elements in the first lens group to be three it is preferable that the 1A lens group G1A is composed of only one positive lens element and the 1B lens group G1B is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object and a positive lens having a convex surface facing to the object. The construction is effective to make the zoom lens system simple, compact, and cheep.

Since the focusing lens group, which is the 1B lens group G1B, is composed of a negative lens and a positive lens, it becomes possible to correct spherical aberration and chromatic aberration, so that variation in spherical aberration and chromatic aberration upon focusing can be suppressed.

In the zoom lens system according to the first embodiment of the present invention, it is preferable to satisfy the following conditional expressions (8) and (9): 50<ν1A  (8) 35<ν1 BP−ν1 BN  (9) where ν1A denotes Abbe number of the positive lens in the 1A lens group G1A at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.

Conditional expression (8) defines an appropriate range of Abbe number of the positive lens consisting of the 1A lens group G1A. When the value ν1A is equal to or falls below the lower limit of conditional expression (8), variation in chromatic aberration upon focusing becomes large, s that it is undesirable. In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (8) is set to 60.

Conditional expression (9) defines an appropriate range of difference between Abbe number of the positive lens and that of the negative meniscus lens consisting of the 1B lens group G1B. When the value ν1BP−ν1BN is equal to or falls below the lower limit of conditional expression (9), variation in chromatic aberration upon focusing and zooming becomes large, so that it is undesirable. In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (9) is set to 40.

Furthermore, it is preferable that the negative meniscus lens and the positive lens in the 1B lens group are cemented. With this construction, degradation of optical performance or production of ghost images caused by assembling can be reduced.

Each example according to the first embodiment of the present invention is explained with reference to accompanying drawings.

EXAMPLE 1

FIG. 1 is a diagram showing a sectional view of a zoom lens system according to Example 1 of a first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 1, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.

The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a double concave negative lens.

The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

Various values associated with Example 1 are listed in Table 1. In [Specifications], f denotes the focal length, FNO denotes the f-number, and 2ω denotes the angle of view. In [Lens Data], the first column is the surface number counted in order from the object side, the second column r denotes the radius of curvature, the third column d denotes the distance along the optical axis between the lens surfaces, and the fourth column ν denotes Abbe number at d-line (λ=587.6 nm) and the fifth column n denotes refractive index at d-line (λ=587.6 nm). In the second column r, reference symbol “∞” denotes a plane. In the fifth column, refractive index of the air 1.00000 is omitted. In [Variable Distances], f denotes the focal length, M denotes the shooting magnification, D0 denotes the distance between the object and the first lens surface, R denotes a distance between the object and the image plane, and Bf denotes the back focal length. In [Values for Conditional Expressions], values for respective conditional expressions are shown.

In the tables for various values, “mm” is generally used for the unit of length such as the focal length, the radius of curvature, and the distance between optical surfaces. However, since an optical system proportionally enlarged or reduced its dimension can be obtained similar optical performance, the unit is not necessary to be limited to “mm” and any other suitable unit can be used. The explanation of reference symbols is the same in the other examples and duplicated explanations are omitted.

TABLE 1 [Specifications] f = 71.40 135.20 294.00 FNO =  3.98  4.42  5.83 2ω = 34.26°  17.57°  8.19° [Lens Data] r d ν n 1 401.1292 3.4320 64.14 1.516330 2 −401.1292 (d2) 3 73.7120 1.8000 28.46 1.728250 4 49.4588 9.2239 81.54 1.496999 5 −634.7712 (d5) 6 −569.6277 1.4000 46.57 1.804000 7 65.8130 2.9470 8 −66.3802 1.4000 49.34 1.743198 9 37.4535 4.4348 23.78 1.846660 10 −157.1502 1.2424 11 −56.4033 1.4000 46.57 1.804000 12 457.6562 (d12) 13 ∞ 1.0000 Aperture Stop S 14 174.8883 4.0762 60.08 1.639999 15 −54.3627 0.2000 16 52.6528 6.0766 81.54 1.496999 17 −40.7675 1.4000 34.97 1.800999 18 1440.7843 0.2000 19 33.5705 3.5534 61.13 1.589130 20 93.9894 (d20) 21 479.6438 1.4000 23.78 1.846660 22 43.7293 4.5629 59.84 1.522494 23 −51.1261 3.0000 24 1129.8061 3.6174 29.23 1.721507 25 −22.8122 1.4000 47.93 1.717004 26 29.6916 4.4859 27 35.9110 3.4607 33.79 1.647689 28 −167.9338 4.3753 29 −22.4279 1.4000 46.57 1.804000 30 −45.1019 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40001 135.19966 294.00012 D0 ∞ ∞ ∞ d2 13.96876 13.96876 13.96876 d5 1.50000 30.16863 45.04078 d12 26.95417 16.63929 1.00000 d20 15.26706 15.23225 16.01169 B.f. 45.82163 54.27048 80.82164 R ∞ ∞ ∞ (Closest Shooting Distance) M −0.05763 −0.11156 −0.24806 D0 1325.0000 1298.2322 1271.6687 d2 1.45642 1.18529 0.90427 d5 14.01234 42.95210 58.10527 d12 26.95417 16.63929 1.00000 d20 15.26706 15.23225 16.01169 B.f. 45.82163 54.27048 80.82164 R 1500.0000 1500.0000 1500.0000 [Values for Conditional Expressions] (1) f1/fw = 1.680 (2) f2/fw = −0.405 (3) f1A/f1B = 2.335 (4) DAB/fw = 0.196 (5) f3/fw = 0.503 (6) f4/fw = −1.060 (7) (D34w − D34t) = −0.010 (8) ν1A = 64.14 (9) ν1BP − ν1BN = 53.08

FIGS. 2A and 2B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 3A and 3B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 4A and 4B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

In respective graphs, FNO denotes the f-number, Y denotes an image height, and D, G denote aberration curves for d-line (λ=587.6 nm) and g-line (λ=435.8 nm), respectively. In graphs showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. In the following Examples, the same reference symbols as Example 1 are used.

As is apparent from respective graphs, the zoom lens system according to Example 1 of the first embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 2

FIG. 5 is a diagram showing a sectional view of a zoom lens system according to Example 2 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 5, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.

The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a double convex positive lens, a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

Various values associated with Example 2 are listed in Table 2.

TABLE 2 [Specifications] f = 71.40 135.20 294.00 FNO =  3.92  4.34  5.79 2ω = 34.01°  17.48°  8.17° [Lens Data] r d ν n 1 393.7797 3.4666 64.14 1.516330 2 −393.7797 (d2) 3 72.1379 1.8000 28.46 1.728250 4 48.5919 9.3212 81.54 1.496999 5 −673.5520 (d5) 6 −371.5827 1.4000 46.57 1.804000 7 57.6115 3.0775 8 −66.8503 1.4000 49.34 1.743198 9 39.7971 4.4329 23.78 1.846660 10 −120.0368 1.3565 11 −48.2268 1.4000 46.57 1.804000 12 −623.8156 (d12) 13 ∞ 1.0000 Aperture Stop S 14 171.0600 4.2202 60.08 1.639999 15 −51.8912 0.2000 16 53.6971 5.9454 81.54 1.496999 17 −42.4415 1.4000 34.97 1.800999 18 798.2716 0.2000 19 34.9966 3.3788 61.13 1.589130 20 91.1723 (d20) 21 224.4236 1.4000 23.78 1.846660 22 39.7038 3.2867 59.84 1.522494 23 −225.6684 6.3172 24 337.2025 3.1647 27.79 1.740769 25 −33.6532 0.2000 26 −34.9705 1.4000 46.57 1.804000 27 41.8882 3.6016 28 48.8184 3.6441 33.79 1.647689 29 −72.7425 10.5386 30 −22.2604 1.4000 46.57 1.804000 31 −42.1654 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40227 135.19993 294.00037 D0 ∞ ∞ ∞ d2 13.53509 13.53509 13.53509 d5 1.60134 30.08411 44.43064 d12 26.58593 16.43870 1.00000 d20 14.32441 14.04027 14.43188 B.f. 40.00116 48.12784 75.00135 R ∞ ∞ ∞ (Closest Shooting Distance) M −0.05757 −0.11137 −0.24756 D0 1325.0001 1298.8220 1272.6491 d2 1.42931 1.17314 0.90588 d5 13.70712 42.44606 57.05985 d12 26.58593 16.43870 1.00000 d20 14.32441 14.04027 14.43188 B.f. 40.00116 48.12784 75.00135 R 1500.0000 1500.0000 1500.0000 [Values for Conditional Expressions] (1) f1/fw = 1.653 (2) f2/fw = −0.402 (3) f1A/f1B = 2.326 (4) DAB/fw = 0.190 (5) f3/fw = 0.513 (6) f4/fw = −1.039 (7) (D34w − D34t) = −0.002 (8) ν1A = 64.14 (9) ν1BP − ν1BN = 53.08

FIGS. 6A and 6B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 7A and 7B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 8A and 8B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 2 of the first embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 3

FIG. 9 is a diagram showing a sectional view of a zoom lens system according to Example 3 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 9, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.

The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a double convex positive lens a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

Various values associated with Example 3 are listed in Table 3.

TABLE 3 [Specifications] f = 71.40 134.90 294.00 FNO =  4.00  4.40  5.87 2ω = 34.03°  17.50°  8.17° [Lens Data] r d ν n 1 14220.5510 2.7079 64.14 1.516330 2 −321.5792 (d2) 3 69.9601 1.8000 34.97 1.800999 4 46.3766 0.2000 5 45.9671 11.3706 81.54 1.496999 6 −419.6274 (d6) 7 −579.1168 1.4000 46.57 1.804000 8 63.8363 3.4452 9 −52.7313 1.4000 49.34 1.743198 10 48.3987 4.2542 23.78 1.846660 11 −107.9428 0.8861 12 −61.0721 1.4000 46.57 1.804000 13 −623.8156 (d13) 14 ∞ 1.0000 Aperture Stop S 15 166.9626 3.9296 60.08 1.639999 16 −58.2127 0.2000 17 57.0867 5.4967 81.54 1.496999 18 −46.6872 1.4000 34.97 1.800999 19 1396.9076 0.2000 20 34.3256 3.4395 61.13 1.589130 21 91.8543 (d21) 22 203.1166 1.4000 23.78 1.846660 23 40.7958 3.2583 59.84 1.522494 24 −258.7153 7.3113 25 302.9723 3.0588 27.79 1.740769 26 −35.3253 0.2000 27 −36.4959 1.4000 46.57 1.804000 28 40.5142 4.9030 29 51.7471 3.3861 33.79 1.647689 30 −82.2838 9.1961 31 −22.3825 1.4000 46.57 1.804000 32 −41.2791 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.39992 134.89970 293.99916 D0 ∞ ∞ ∞ d2 15.80731 15.80731 15.80731 d6 1.50000 34.04735 50.19310 d13 29.37034 18.20055 1.00000 d21 13.27877 12.96969 12.95602 B.f. 40.00001 47.68741 74.99998 R ∞ ∞ ∞ (Closest Shooting Distance) M −0.05859 −0.11340 −0.25277 D0 1320.0000 1291.2441 1265.0000 d2 1.48390 1.14166 0.81459 d6 15.82341 48.71300 65.18582 d13 29.37034 18.20055 1.00000 d21 13.27877 12.96969 12.95602 B.f. 40.00001 47.68741 74.99998 R 1500.0000 1500.0000 1500.0000 [Values for Conditional Expressions] (1) f1/fw = 1.823 (2) f2/fw = −0.449 (3) f1A/f1B = 3.778 (4) DAB/fw = 0.221 (5) f3/fw = 0.521 (6) f4/fw = −0.928 (7) (D34w − D34t) = 0.005 (8) ν1A = 64.14 (9) ν1BP − ν1BN = 46.57

FIGS. 10A and 10B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 11A and 11B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 12A and 12B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 3 of the first embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 4

FIG. 13 is a diagram showing a sectional view of a zoom lens system according to Example 4 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 13, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.

Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a negative meniscus lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a fixed stop S2, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged to the object side of the 31 lens group G31 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Various values associated with Example 4 is listed in Table 4.

TABLE 4 [Specifications] f = 71.40 135.00 294.00 FNO =  4.64  4.85  5.88 2ω = 34.46°  17.55°  8.20° [Lens Data] r d ν n 1 340.6588 4.2 64.14 1.51633 2 −340.659 (d2) 3 65.1639 1.8 26.3 1.784696 4 45.8381 8.8 81.61 1.496999 5 −1308.92 (d5) 6 −271.25 1.4 49.61 1.772499 7 71.7854 1.3 8 −566.934 1.4 49.61 1.772499 9 24.4437 4.7 23.78 1.84666 10 133.0962 3.75 11 −46.0918 1.4 49.61 1.772499 12 1927.614 (d12) 13 ∞ 2 Aperture Stop S 14 188.6747 3.4 60.09 1.639999 15 −72.245 0.2 16 73.7218 6 81.61 1.496999 17 −38.1983 1.4 34.96 1.800999 18 −154.661 0.2 19 32.255 4.2 52.42 1.517417 20 143.854 7.9 21 333.5741 1.3 23.78 1.84666 22 54.3293 4.1 70.24 1.48749 23 −89.5707 10.2 24 256.9205 3.6 25.43 1.805181 25 −35.5686 1.2 39.59 1.804398 26 35.5686 3.4 27 ∞ 3.1 Fixed Stop S2 28 47.0802 4 34.47 1.639799 29 −96.8946 2.4 30 −23.3234 1.2 49.61 1.772499 31 −42.5579 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.39993 134.99982 294.00047 D0 ∞ ∞ ∞ d2 13.43865 13.43865 13.43865 d5 2.49989 31.01849 43.01129 d12 28.21141 18.59271 2.50011 B.f. 53.40008 57.30852 87.10064 R ∞ ∞ ∞ (Closest Shooting Distance) M −0.05775 −0.11125 −0.24755 D0 1313.9000 1291.0916 1265.3993 d2 2.36289 2.15893 1.91994 d5 13.57565 42.29821 54.53000 d12 28.21141 18.59271 2.50011 B.f. 53.40008 57.30852 87.10064 R 1500.0000 1500.0000 1500.0000 [Values for Conditional Expressions] (1) f1/fw = 1.563 (2) f2/fw = −0.368 (3) f1A/f1B = 2.051 (4) DAB/fw = 0.188 (5) f3/fw = 0.525 (8) ν1A = 64.14 (9) ν1BP − ν1BN = 55.31

FIGS. 14A and 14B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 15A and 15B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 16A and 16B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 4 of the first embodiment shows superb optical performance correcting various aberrations.

[Second Embodiment]

A zoom lens system according to a second embodiment of the present invention is explained below.

The zoom lens system with a vibration reduction mechanism according to the second embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power. When the state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and fourth lens group varies. The construction is effective for shortening the total lens length.

The fourth lens group is composed of, in order from the object, a 41 lens group, a 42 lens group having negative refractive power, and a 43 lens group. At least one of the 41 lens group and the 43 lens group has positive refractive power. By moving only the 42 lens group perpendicular to the optical axis, image blur on an image plane caused by a camera shake can be reduced.

With constructing the fourth lens group having negative refractive power, the effective diameter of the fourth lens group can be small relative to those of the first lens group through the third lens group. Moreover, by constructing power arrangement of the fourth lens group with positive-negative-positive, positive-negative-negative, or negative-negative-positive, the effective diameter of the 42 lens group, which is the vibration reduction lens group, can be small. Accordingly, the vibration reduction mechanism can be compact, so that it is effective for the zoom lens system as a whole to be compact. By constructing in this manner, degradation of optical performance caused by moving the 42 lens group perpendicular to the optical axis can be reduced.

In the zoom lens system according to the second embodiment of the present invention, the following conditional expression (10) is preferably satisfied: 0.10<f42/f4<0.90  (10) where f4 denotes the focal length of the fourth lens group, and f42 denotes the focal length of the 42 lens group.

Conditional expression (10) defines an appropriate range of the focal length of the 42 lens group suitable for vibration reduction. When the ratio f42/f4 is equal to or exceeds the upper limit of conditional expression (10), negative refractive power of the 42 lens group becomes weak, so that an amount of decentering of the 42 lens required for vibration reduction becomes large. Accordingly, the vibration reduction mechanism becomes large, so that it becomes difficult to suppress the whole dimension of the zoom lens system to be compact. On the other hand, when the ratio f42/f4 is equal to or falls below the lower limit of conditional expression (10), negative refractive power of the 42 lens group becomes large. Accordingly, production of various aberrations in the 42 lens group becomes large, so that production of decentering aberration upon moving the 42 lens group for vibration reduction becomes large.

In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (10) to 0.25 and the upper limit to 0.70.

In the zoom lens system according to the second embodiment of the present invention, the following conditional expressions (11) and (12) are preferably satisfied: −2.10<f4/fw<−0.70  (11) −2.10<(1/f41+1/f43)·f4<−0.40  (12) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f41 denotes the focal length of the 41 lens group, and f43 denotes the focal length of the 43 lens group.

Conditional expression (11) defines an appropriate range of the focal length of the fourth lens group suitable for miniaturizing the total length of the zoom lens system and the effective diameter of the fourth lens group. When the ratio f4/fw is equal to or exceeds the upper limit of conditional expression (11), negative refractive power of the fourth lens group becomes excessively large, so that it becomes difficult to satisfactorily correct aberrations. On the other hand, when the ratio f4/fw is equal to or falls below the lower limit of conditional expression (11), negative refractive power of the fourth lens group becomes small, so that it becomes difficult to miniaturize the total length of the zoom lens system and the effective diameter of the fourth lens group.

In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (11) to −2.00 and the upper limit to −0.90.

Conditional expression (12) defines an appropriate range of the summation of refractive power of the 41 lens group and that of the 43 lens group suitable for miniaturizing the effective diameter of the 42 lens group. When the value (1/f41+1/f43)·f4 is equal to or falls below the lower limit of conditional expression (12), the summation of refractive power of the 41 lens group and that of the 43 lens group becomes large, so that negative refractive power of the 42 lens group has to be large in order to obtain negative refractive power of the fourth lens group as a whole. As a result, production of various aberrations in the 42 lens group becomes large, so that production of decentering aberration caused by moving the 42 lens group for vibration reduction becomes large. On the other hand, when the value (1/f41+1/f43)·f4 is equal to or exceeds the upper limit of conditional expression (12), the summation of refractive power of the 41 lens group and that of the 43 lens group becomes small, so that the effect of converging the light flux becomes weak. As a result, miniaturizing the effective diameter of the 42 lens group becomes insufficient.

In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (12) to −2.00 and the upper limit to −0.50.

Moreover, the zoom lens system is preferably constructed such that when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fourth lens group are moved to the object side. With this construction, the total lens length of the zoom lens system in the wide-angle end state can be compact.

Furthermore, it is preferable that the 41 lens group includes at least one positive lens element, the 42 lens group includes at least one positive lens element and at least one negative lens element, and the 43 lens group includes at least one positive lens element. With this construction, decentering aberration upon vibration reduction can be corrected well.

Furthermore, in the zoom lens system according to the second embodiment of the present invention, the 41 lens group includes, in order from the object, a negative lens having a concave surface facing to the object, a positive lens having a convex surface facing to the object, and the following conditional expression (13) is preferably satisfied: 0.20<n41N−n41P  (13) where n41N denotes refractive index of the negative lens in the 41 lens group at d-line (λ=578.6 nm), and n41P denotes refractive index of the positive lens in the 41 lens group at d-line.

Conditional expression (13) is for satisfactorily correcting decentering aberration upon vibration reduction. When the value n41N−n41P is equal to or falls below the lower limit of conditional expression (13), it becomes difficult to correct decentering aberration upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (13) to 0.25.

In the zoom lens system according to the second embodiment of the present invention, the 42 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (14) is preferably satisfied: 10.0<ν42N−ν42P  (14) where ν42N denotes Abbe number of the double concave negative lens in the 42 lens group at d-line (λ=578.6 nm), and ν42P denotes Abbe number of the positive lens in the 42 lens group at d-line.

Conditional expression (14) is for satisfactorily correcting decentering aberrations upon vibration reduction. When the value ν42N−ν42P is equal to or falls below the lower limit of conditional expression (14), it becomes difficult to correct lateral chromatic aberration produced by decentering upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (14) to 12.0.

In the zoom lens system according to the second embodiment of the present invention, it is preferable that the zoom lens system consists only of the first lens group, the second lens group, the third lens group, and the fourth lens group. By arranging no lens group with refractive power to the image side of the fourth lens group, the zoom lens system can be simple.

In the zoom lens system according to the second embodiment of the present invention, it is preferable that a fifth lens group having positive refractive power is arranged to the image side of the fourth lens group. With this construction, the degree of freedom for correcting aberration increases, so that various aberrations can be corrected easily.

Moreover, it is preferable that the first lens group as a whole is moved to the object upon focusing from infinity to a close-range object.

Furthermore, it is preferable that the second lens group as a whole is moved to the object upon focusing from infinity to a close-range object, and the following conditional expression (15) is preferably satisfied: −0.98<M2t<−0.8  (15) where M2t denotes magnification of the second lens group in the telephoto end state.

When the value M2t is equal to or falls below the lower limit of conditional expression (15), the magnification becomes nearly to −1, so that focusing cannot be carried out. On the other hand, when the value M2t is equal to or exceeds the upper limit of conditional expression (15), it becomes difficult to obtain zoom ratio of about four. In order to further secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (15) to −0.90.

In the zoom lens system according to the second embodiment of the present invention, it is preferable that the first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power, and focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object.

Each example of the second embodiment is explained below with reference to accompanying drawings.

EXAMPLE 5

FIG. 17 is a diagram showing a sectional view of a zoom lens system according to Example 5 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 17, a zoom lens system with a vibration reduction mechanism according to Example 5 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 increases.

The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.

The second lens group G2 is composed of, in order from the object, a cemented lens constructed by a positive meniscus lens having a concave surface facing to the object cemented with a double concave negative lens, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens having a concave surface facing to the object, and a positive meniscus lens having a convex surface facing to the object.

An aperture stop S is arranged between a double convex positive lens and a cemented lens in the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having negative refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a positive meniscus lens L42 having a convex surface facing to the object. The 42 lens group G42 is composed of, in order from the object, a positive meniscus lens L43 having a concave surface facing to the object, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a positive meniscus lens L46 having convex surface facing to the object.

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the first lens group G1 to the object.

In order to correct an image movement corresponding to a rotational angle of θ by a lens system having the focal length of f, and vibration reduction coefficient (the ratio of the moving amount of the image to the moving amount of the vibration reduction lens group upon carrying out vibration reduction) of K, the vibration reduction lens group may be moved by the amount of (f·tan θ)/K perpendicular to the optical axis. This relation is the same in the following examples and duplicated explanation is omitted.

In the wide-angle end state (W) of Example 5 of the second embodiment, vibration reduction coefficient K is 1.206, and the focal length f is 71.50 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.311 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).

Various values associated with Example 5 of the second embodiment of the present invention is listed in Table 5.

In [Moving Amount upon Focusing], δ1 denotes a moving amount of the first lens group G1 to the object side focusing at the shooting distance of 1500 (mm).

TABLE 5 [Specifications] f = 71.50 134.90 294.00 FNO =  4.43  4.78  5.83 2ω = 34.69°  17.82°  8.25° [Lens Data] r d ν n 1 106.9922 1.4000 30.13 1.698947 2 63.9533 8.5690 81.54 1.496999 3 −244.9710 0.2000 4 126.9321 2.8438 53.20 1.693501 5 216.9031 (d5) 6 −811.4085 3.2995 23.78 1.846660 7 −45.9839 1.0000 60.08 1.639999 8 53.9629 3.6848 9 −41.3222 1.0000 46.57 1.804000 10 403.6997 (d10) 11 117.0360 3.4927 46.57 1.804000 12 −100.5857 1.5000 13 ∞ 1.0480 Aperture Stop S 14 52.7514 5.2513 81.54 1.496999 15 −62.0004 1.0000 34.97 1.800999 16 −445.4607 0.2000 17 37.5205 2.9883 81.54 1.496999 18 74.7018 (d18) 19 52.6572 1.4000 23.78 1.846660 20 16.3065 4.5499 45.78 1.548141 21 76.4617 12.6826 22 −126.2398 3.9806 28.46 1.728250 23 −20.5284 0.2000 24 −20.6563 1.4000 46.57 1.804000 25 46.6744 4.6040 26 2036.2018 2.3561 29.23 1.721507 27 −113.7498 0.2000 28 47.0423 3.6545 34.97 1.800999 29 343.9390 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] f 71.50000 134.90000 294.00000 d5 1.55195 36.01475 55.38418 d10 34.15302 21.90257 1.00000 d18 18.78991 19.40071 22.11070 B.f. 42.99999 49.92314 69.00000 [Moving Amount upon Focusing] f 71.500 134.900 294.000 δ1 14.446 14.822 15.090 [Values for Conditional Expressions] (10) f42/f4 = 0.356 (11) f4/fw = −1.483 (12) (1/f41 + 1/f43) · f4 = −1.309 (13) n41N − n41P = 0.298 (14) ν42N −ν42P = 28.11 (15) M2t = —

FIGS. 18A and 18B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 19 shows various aberrations of the zoom lens system according to Example 5 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 20A and 20B show various aberrations of the zoom lens system according to Example 5 of the first embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 5 of the second embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 6

FIG. 21 is a diagram showing a sectional view of a zoom lens system according to Example 6 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 21, a zoom lens system with a vibration reduction mechanism according to Example 6 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies.

The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a negative meniscus lens having a concave surface facing to the object.

The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a double convex positive lens L43, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.

In the wide-angle end state (W) of Example 6 of the second embodiment, vibration reduction coefficient K is 1.054, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.355 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).

Various values associated with Example 6 of the second embodiment of the present invention is listed in Table 6.

In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).

TABLE 6 [Specifications] f = 71.40 134.90 294.00 FNO =  4.03  4.61  5.83 2ω = 34.73°  17.96°  8.29° [Lens Data] r d ν n 1 110.3430 1.8000 29.23 1.721507 2 69.3904 7.9665 81.54 1.496999 3 −294.8326 0.2000 4 122.8189 2.6850 58.55 1.651597 5 181.6203 (d5) 6 −3611.5709 1.4000 47.82 1.756998 7 49.7266 0.4871 8 57.7644 5.3831 23.78 1.846660 9 −42.0999 1.4000 36.26 1.620041 10 53.1079 4.0773 11 −38.0886 1.4000 34.97 1.800999 12 −502.7476 (d12) 13 ∞ 1.0000 Aperture Stop S 14 97.5978 3.6622 58.55 1.651597 15 −81.8300 0.2000 16 48.0953 4.9666 81.54 1.496999 17 −62.0949 1.4000 34.97 1.800999 18 268.7785 0.2000 19 38.8902 3.2836 55.53 1.696797 20 54.2852 (d20) 21 78.0173 2.0000 23.78 1.846660 22 24.6186 3.7355 64.14 1.516330 23 −185.3460 3.0000 24 176.2975 4.6442 27.79 1.740769 25 −25.6263 0.2072 26 −25.4689 1.4000 40.92 1.806098 27 35.9916 3.3747 28 32.3977 4.1609 30.13 1.698947 29 −160.3892 4.5174 30 −28.3572 1.4000 61.13 1.589130 31 −96.5409 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] f 71.40045 134.89998 293.99991 d5 4.92513 37.53918 59.35524 d12 35.77592 21.59232 1.00000 d20 24.34764 24.24866 24.69346 B.f. 40.00576 51.49527 75.00890 [Moving Amount upon Focusing] f 71.400 134.900 294.000 δ2 2.762 6.788 17.131 [Values for Conditional Expressions] (10) f42/f4 = 0.366 (11) f4/fw = −1.891 (12) (1/f41 + 1/f43) · f4 = −1.866 (13) n41N − n41P = 0.330 (14) ν42N − ν42P = 13.13 (15) M2t = −0.950

FIGS. 22A and 22B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 23 shows various aberrations of the zoom lens system according to Example 6 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 24A and 24B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 6 of the second embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 7

FIG. 25 is a diagram showing a sectional view of a zoom lens system according to Example 7 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 25, a zoom lens system with a vibration reduction mechanism according to Example 7 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 increases.

The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.

The second lens group G2 is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having negative refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a double convex positive lens L43, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.

In the wide-angle end state (W) of Example 7 of the second embodiment, vibration reduction coefficient K is 1.059, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.353 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).

Various values associated with Example 7 of the second embodiment of the present invention is listed in Table 7.

In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).

TABLE 7 [Specifications] f = 71.40 134.90 294.00 FNO =  3.99  4.52  5.75 2ω = 34.74°  17.97°  8.30° [Lens Data] r d ν n 1 92.3146 1.8000 34.97 1.800999 2 60.1527 9.0323 81.54 1.496999 3 −249.0431 0.2000 4 80.8726 2.7760 70.23 1.487490 5 103.7057 (d5) 6 67.7254 1.4000 28.46 1.728250 7 34.1420 4.4733 8 −56.4538 1.4000 60.29 1.620411 9 40.9332 3.9004 23.78 1.846660 10 −339.3969 1.7837 11 −50.6122 1.4000 51.47 1.733997 12 −623.8156 (d12) 13 ∞ 1.0000 Aperture Stop S 14 102.7196 3.8033 60.08 1.639999 15 −83.7403 0.2000 16 51.7820 5.2043 81.54 1.496999 17 −63.2478 1.4000 34.97 1.800999 18 327.7985 0.2000 19 41.6150 3.5656 46.57 1.804000 20 67.4980 (d20) 21 65.4401 1.4000 23.78 1.846660 22 20.9137 3.9266 70.23 1.487490 23 −450.5603 4.1017 24 167.1060 3.8379 28.46 1.728250 25 −25.2899 0.2000 26 −25.2945 1.4000 40.92 1.806098 27 36.0693 4.0874 28 32.4764 4.5076 30.13 1.698947 29 −134.5935 4.2066 30 −31.0368 1.4000 60.08 1.639999 31 −108.8255 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] f 71.40000 134.90000 294.00000 d5 4.03725 36.57205 57.18679 d12 34.46408 20.96534 1.00000 d20 23.89184 23.91724 24.20639 B.f. 40.00000 50.65460 74.99996 [Moving Amount upon Focusing] f 71.400 134.900 294.000 δ2 2.539 6.520 16.557 [Values for Conditional Expressions] (10) f42/f4 = 0.505 (11) f4/fw = −1.358 (12) (1/f41 + 1/f43) · f4 = −1.079 (13) n41N = n41P = 0.359 (14) ν42N − ν42P = 12.46 (15) M2t = −0.961

FIGS. 26A and 26B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 27 shows various aberrations of the zoom lens system according to Example 7 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 28A and 28B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.150, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 7 of the second embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 8

FIG. 29 is a diagram showing a sectional view of a zoom lens system according to Example 8 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 29, a zoom lens system with a vibration reduction mechanism according to Example 8 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.

An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens L43 cemented with a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 8 of the second embodiment, vibration reduction coefficient K is 1.395, and the focal length f is 71.40 (mm), so that the image rotation of 0.300 can be corrected by moving the 42 lens group G42 by the amount of 0.268 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.261, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.340 (mm).

Various values associated with Example 8 of the second embodiment of the present invention is listed in Table 8.

In [Moving Amount upon Focusing], δ1B denotes a moving amount of the 1B lens group G1B to the object side focusing at the shooting distance of 1500 (mm).

TABLE 8 [Specifications] f = 71.40 135.20 294.00 FNO =  3.98  4.42  5.83 2ω = 34.26°  17.57°  8.19° [Lens Data ] r d ν n 1 401.1292 3.4320 64.14 1.516330 2 −401.1292 (d2) 3 73.7120 1.8000 28.46 1.728250 4 49.4588 9.2239 81.54 1.496999 5 −634.7712 (d5) 6 −569.6277 1.4000 46.57 1.804000 7 65.8130 2.9470 8 −66.3802 1.4000 49.34 1.743198 9 37.4535 4.4348 23.78 1.846660 10 −157.1502 1.2424 11 −56.4033 1.4000 46.57 1.804000 12 457.6562 (d12) 13 ∞ 1.0000 Aperture Stop S 14 174.8883 4.0762 60.08 1.639999 15 −54.3627 0.2000 1.000000 16 52.6528 6.0766 81.54 1.496999 17 −40.7675 1.4000 34.97 1.800999 18 1440.7843 0.2000 19 33.5705 3.5534 61.13 1.589130 20 93.9894 (d20) 21 479.6438 1.4000 23.78 1.846660 22 43.7293 4.5629 59.84 1.522494 23 −51.1261 3.0000 24 1129.8061 3.6174 29.23 1.721507 25 −22.8122 1.4000 47.93 1.717004 26 29.6916 4.4859 27 35.9110 3.4607 33.79 1.647689 28 −167.9338 4.3753 29 −22.4279 1.4000 46.57 1.804000 30 −45.1019 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] f 71.39999 135.19963 294.00017 d2 13.96876 13.96876 13.96876 d5 1.50000 30.16863 45.04078 d12 26.95417 16.63929 1.00000 d20 15.26706 15.23225 16.01169 B.f. 45.82163 54.27048 80.82164 [Moving Amount upon Focusing] f 71.400 135.200 294.000 δ1B 12.512 12.783 13.064 [Values for Conditional Expressions] (10) f42/f4 = 0.579 (11) f4/fw = −1.039 (12) (1/f41 + 1/f43) · f4 = −0.816 (13) n41N − n41P = 0.324 (14) ν42N − ν42P = 18.70 (15) M2t = —

FIGS. 30A and 30B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 31 shows various aberrations of the zoom lens system according to Example 8 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 32A and 32B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 8 of the second embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 9

FIG. 33 is a diagram showing a sectional view of a zoom lens system according to Example 9 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 33, a zoom lens system with a vibration reduction mechanism according to Example 9 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move to the object and the second lens group G2 moves once to the object and, then, moves to an image I such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, a distance between the third lens group G3 and the fourth lens group G4 increases, and a distance between the fourth lens group G4 and the fifth lens group decreases.

The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, and a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens.

The third lens group G3 is composed of, in order from the object, a plano-convex positive lens having a convex surface facing to the image, a double convex positive lens, a negative meniscus lens having a concave surface facing to the object, and a double convex positive lens.

An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having negative refractive power. The 41 lens group G41 is composed of a double convex positive lens L41. The 42 lens group G42 is composed of, in order from the object, a double concave negative lens L42, and a positive meniscus lens L43 having a convex surface facing to the object. The 43 lens group G43 is composed of a negative meniscus lens L44 having a concave surface facing to the object.

The fifth lens group G5 is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.

In the wide-angle end state (W) of Example 9 of the second embodiment, vibration reduction coefficient K is 1.719, and the focal length f is 69.99 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.213 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.284, and the focal length f is 299.93 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.344 (mm).

Various values associated with Example 9 of the second embodiment of the present invention is listed in Table 9.

In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).

TABLE 9 [Specifications] f = 69.99 134.96 299.93 FNO =  4.31  5.28  5.77 2ω = 34.39°  17.94°  8.06° [Lens Data] r d ν n 1 105.7828 1.5000 25.43 1.805180 2 74.2801 7.7806 81.61 1.497000 3 −314.2885 0.5000 4 84.1721 4.0034 81.61 1.497000 5 192.0413 (d5) 6 −289.0462 1.5000 49.61 1.772500 7 37.2942 5.1639 8 −36.2718 1.5000 53.85 1.713000 9 42.3070 3.9288 23.78 1.846660 10 −275.6800 (d10) 11 ∞ 0.5000 Aperture Stop S 12 ∞ 2.5521 49.61 1.772500 13 −91.7378 0.5000 14 44.2611 6.7347 81.61 1.497000 15 −34.2879 0.6605 16 −32.1236 1.5000 37.17 1.834000 17 −239.8905 0.5000 18 48.9662 4.7058 81.61 1.497000 19 −95.8226 (d19) 20 38.7220 5.1115 81.61 1.497000 21 −81.1156 3.8000 22 −1244.0407 1.5000 46.63 1.816000 23 18.1395 0.5544 24 18.4154 3.9902 34.47 1.639800 25 57.0111 3.8499 26 −24.5068 1.5000 49.32 1.743200 27 −42.2340 (d27) 28 106.2163 1.5000 23.78 1.846660 29 36.1752 3.2036 30 51.9898 4.5496 33.04 1.666800 31 −45.3816 3.9985 32 −24.1064 1.5000 46.63 1.816000 33 −36.1573 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] f 69.98593 134.95979 299.92772 d5 7.77097 31.32565 57.66235 d10 25.75941 15.14446 0.50000 d19 3.94280 7.03157 7.76808 d27 10.15139 2.54225 0.50000 B.f. 50.26987 74.11967 85.25814 [Moving Amount upon Focusing] f 69.986 134.960 299.928 δ2 1.324 2.865 12.223 [Values for Conditional Expressions] (10) f42/f4 = 0.484 (11) f4/fw = −1.353 (12) (1/f41 + 1/f43) · f4 = −0.608 (13) n41N − n41P = — (14) ν42N − ν42P = — (15) M2t = −0.973

FIGS. 34A and 34B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 35 shows various aberrations of the zoom lens system according to Example 9 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 36A and 36B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 9 of the second embodiment shows superb optical performance correcting various aberrations.

[Third Embodiment]

A zoom lens system according to a third embodiment of the present invention is explained below.

The zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When the state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The construction is effective for simplifying the construction and shortening the total lens length.

The third lens group G3 is composed of, in order from the object, a 31 lens group having positive refractive power, a 32 lens group having negative refractive power, and a 33 lens group having positive refractive power. Upon detecting a camera shake, vibration reduction is carried out by moving only the 32 lens group perpendicular to the optical axis. By arranging positive refractive power to the 31 lens group and negative refractive power to the 32 lens group, the effective diameter of the 32 lens group can be small relative to those of the first lens group through the 31 lens group. Accordingly, the vibration reduction mechanism can be compact, so that it is effective for the zoom lens system as a whole to be compact. By constructing in this manner, degradation of optical performance caused by moving the 32 lens group perpendicular to the optical axis can be reduced.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expressions (16) through (20) are preferably satisfied: 1.40<f1/fw<2.00  (16) −0.53<f2/fw<−0.32  (17) 0.35<f3/fw<0.65  (18) −2.00<f32/f3<−0.80  (19) −0.20<f3/f33<0.50  (20) where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f3 denotes the focal length of the third lens group, f32 denotes the focal length of the 32 lens group, and f33 denotes the focal length of the 33 lens group.

Conditional expression (16) defines an appropriate range of the focal length of the first lens group. When the ratio f1/fw is equal to or exceeds the upper limit of conditional expression (16), refractive power of the first lens group becomes weak, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f1/fw is equal to or falls below the lower limit of conditional expression (16), refractive power of the first lens group becomes large, so that it becomes difficult to correct spherical aberration and on-axis chromatic aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (16) to 1.50 and the upper limit to 1.90.

Conditional expression (17) defines an appropriate range of the focal length of the second lens group. When the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (17), negative refractive power of the second lens group becomes large, so that it becomes difficult to correct spherical aberration and coma. On the other hand, when the ratio f2/fw is equal to or falls below the lower limit of conditional expression (17), negative refractive power of the second lens group becomes weak, so that it becomes difficult to obtain the zoom ratio of about four. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (17) to −0.50 and the upper limit to −0.35.

Conditional expression (18) defines an appropriate range of the focal length of the third lens group. When the ratio f3/fw is equal to or exceeds the upper limit of conditional expression (18), refractive power of the third lens group becomes weak, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f3/fw is equal to or falls below the lower limit of conditional expression (18), refractive power of the third lens group becomes large, so that it becomes difficult to correct various aberrations as well as spherical aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (18) to 0.40 and the upper limit to 0.60.

Conditional expression (19) defines an appropriate range of the focal length of the 32 lens group. When the ratio f32/f3 is equal to or exceeds the upper limit of conditional expression (19), negative refractive power of the 32 lens group becomes large, so that the ratio of the moving amount of image relative to the moving amount of the 32 lens group upon vibration reduction becomes large. Accordingly, permissible driving error of the 32 lens group upon vibration reduction becomes small, so that it becomes difficult to control the 32 lens group. On the other hand, when the ratio f32/f3 is equal to or falls below the lower limit of conditional expression (19), negative refractive power of the 32 lens group becomes small, so that the ratio of the moving amount of image relative to the moving amount of the 32 lens group upon vibration reduction becomes small. Accordingly, moving amount of the 32 lens group upon vibration reduction becomes large, so that the vibration reduction mechanism becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (19) to −1.85 and the upper limit to −0.90.

Conditional expression (20) defines an appropriate range of the focal length of the 33 lens group. When the ratio f3/f33 is equal to or exceeds the upper limit of conditional expression (20), positive refractive power of the 33 lens group becomes large, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f3/f33 is equal to or falls below the lower limit of conditional expression (20), negative refractive power of the 33 lens group becomes large, so that it becomes difficult to correct coma and distortion. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (20) to −0.15 and the upper limit to 0.40.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the first lens group and the third lens group move to the object when the state of lens group positions varies from the wide-angle end state to the telephoto end state. By construction like this, the total lens length of the zoom lens system in the wide-angle end state can be short, so that the zoom lens system can be compact.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 31 lens group includes at least three positive lens elements and at least one negative lens element, the 32 lens group includes at least one positive lens element and at least one negative lens element, and the 33 lens group includes at least one positive lens element and at least one negative lens element. By constructing like this, decentering aberration caused upon vibration reduction can be satisfactorily corrected.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 31 lens group is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative lens having a concave surface facing to the object, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expressions (21) and (22) are preferably satisfied: 0.20<n31N−n31P  (21) 30.0<ν31P−ν31N  (22) where n31N denotes refractive index of the negative lens in the first cemented lens at d-line (λ=587.6 nm), n31P denotes refractive index of the double convex positive lens in the first cemented lens at d-line, ν31N denotes Abbe number of the negative lens in the first cemented lens at d-line, and ν31P denotes Abbe number of the double convex positive lens in the first cemented lens at d-line.

Conditional expression (21) defines an appropriate range of the difference in refractive indices between the double convex positive lens and the negative lens in the first cemented lens. When the difference n31N−n31P is equal to or falls below the lower limit of conditional expression (21), it becomes difficult to satisfactorily correct spherical aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (21) to 0.25.

Conditional expression (22) defines an appropriate range of the difference in Abbe numbers between the double convex positive lens and the negative lens in the first cemented lens. When the difference ν31P−ν31N I equal to or falls below the lower limit of conditional expression (22), it becomes difficult to satisfactorily correct lateral chromatic aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (22) to 35.0.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 32 lens group is composed of, in order from the object, a positive lens having a convex surface facing to the object, and a double concave negative lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (23) is preferably satisfied: 10.0<ν32N−ν32P  (23) where ν32N denotes Abbe number of the double concave negative lens in the 32 lens group at d-line (λ=587.6 nm), and ν32P denotes Abbe number of the positive lens in the 32 lens group at d-line.

Conditional expression (23) defines an appropriate range of the difference in Abbe numbers between the double concave negative lens and the positive lens in the 32 lens group. When the difference ν32N−ν32P is equal to or falls below the lower limit of conditional expression (23), it becomes difficult to correct lateral chromatic aberration caused by decentering upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (23) to 12.0.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 32 lens group is composed of, in order from the object, a cemented lens constructed by a positive lens having a convex surface facing to the image cemented with a double concave negative lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (24) is preferably satisfied: −2.00<(r32R+r32F)/(r32R−r32F)<−0.70  (24) where r32F denotes the radius of curvature of the object side surface of the positive lens in the 32 lens group, r32R denotes the radius of curvature of the image side surface of the double concave negative lens in the 32 lens group.

Conditional expression (24) defines an appropriate range of the shape of the cemented lens in the 32 lens group. When the value (r32R+r32F)/(r32R−r32F) exceeds the upper limit of conditional expression (24) or falls below the lower limit of conditional expression (24), production of decentering aberration caused upon vibration reduction becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (24) to −1.90 and the upper limit to −0.80.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (25) is preferably satisfied: 0.40<r32S/f32<0.90  (25) where r32S denotes the radius of curvature of the cemented surface of the cemented lens in the 32 lens group, and f32 denotes the focal length of the 32 lens group.

Conditional expression (25) defines an appropriate range of the radius of curvature of the cemented surface of the cemented lens in the 32 lens group. When the ratio r32S/f32 exceeds the upper limit of conditional expression (25) or falls below the lower limit of conditional expression (25), production of decentering aberration caused upon vibration reduction becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (25) to 0.45 and the upper limit to 0.85.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the zoom lens system consists only of a first lens group, a second lens group, and a third lens group. By arranging no lens group with refractive power to the image side of the third lens group, the zoom lens system can be simple.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the first lens group is composed of, in order from the object, it is preferable that a 1A lens group having positive refractive power and a 1B lens group having positive refractive power, and focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object.

In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (26) is preferably satisfied: 1.70<f1A/f1B<4.00  (26) where f1A denotes the focal length of the 1A lens group, and f1B denotes the focal length of the 1B lens group.

Conditional expression (26) defines an appropriate range of the ratio of the focal length of the 1A lens group to that of the 1B lens group. When the ratio f1A/f1B is equal to or exceeds the upper limit of conditional expression (26), refractive power of the 1B lens group becomes small, so that variation in various aberrations upon focusing becomes large. On the other hand, when the ratio f1A/f1B is equal to or falls below the lower limit of conditional expression (26), refractive power of the 1A lens group becomes small, so that moving amount of the 1A lens group upon focusing becomes large. Accordingly, the zoom lens system becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (26) to 1.90 and the upper limit to 3.50.

Each example according to the third embodiment of the present invention is explained below with reference to accompanying drawings.

EXAMPLE 10

FIG. 37 is a diagram showing a sectional view of a zoom lens system according to Example 10 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 37, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged between the positive meniscus lens and the second cemented lens in the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 10 of the third embodiment, vibration reduction coefficient K is 1.47, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.254 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.68, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.287 (mm).

Various values associated with Example 10 of the third embodiment of the present invention is listed in Table 10.

In [Moving Amount upon Focusing], δ1B denotes a moving amount of the 1B lens group G1B to the object side focusing at the shooting distance of 1500 (mm).

TABLE 10 [Specifications] f = 71.40 134.90 294.00 FNO =  4.10  4.28  5.79 2ω = 22.50°  11.75°  5.44° [Lens Data ] r d ν n 1 485.2517 3.3856 64.14 1.516330 2 −485.2517 (d2) 3 74.6948 2.5000 26.52 1.761821 4 50.2473 8.5338 70.23 1.487490 5 −397.6433 (d5) 6 −445.5319 1.4000 49.60 1.772499 7 121.5057 1.7612 8 −139.8007 1.4000 49.60 1.772499 9 31.4033 4.4544 23.78 1.846660 10 195.1690 2.3037 11 −63.0020 1.4000 49.60 1.772499 12 863.7974 (d12) 13 209.2396 3.4957 51.47 1.733997 14 −78.5539 0.2000 15 53.3010 6.1013 81.54 1.496999 16 −47.6905 1.4000 34.97 1.800999 17 743.9564 0.2000 18 31.2964 4.0974 60.64 1.603112 19 86.8951 12.4001 20 ∞ 1.0000 Aperture Stop S 21 67.3937 1.3000 23.78 1.846660 22 26.7354 5.4922 70.23 1.487490 23 −88.9999 5.5185 24 1974.4906 3.7052 26.52 1.761821 25 −26.6771 1.2000 49.60 1.772499 26 26.6771 3.2607 27 29.4872 3.9533 34.47 1.639799 28 −93.8522 2.2384 29 −21.9460 1.2000 49.60 1.772499 30 −59.2566 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40000 134.90024 294.00000 d2 16.01875 16.01875 16.01875 d5 2.00000 31.41839 42.84564 d12 32.45495 19.43707 2.00000 B.f. 40.62478 47.41150 80.62502 [Moving Amount upon Focusing] f 71.40000 134.90024 294.00000 δ1B 13.70747 13.96627 14.28274 [Values for Conditional Expressions] (16) f1/f2 = 1.773 (17) f2/fw = −0.463 (18) f3/fw = 0.500 (19) f32/f3 = −0.9678 (20) f3/f33 = 0.306 (21) n31N − n31P = 0.304 (22) ν31P − ν31N = 46.57 (23) ν32N −ν32P = 23.08 (24) (r32R + r32F)/(r32R −r32F) = −1.027 (25) r32S/f32 = 0.772 (26) f1A/f1B = 2.819

FIGS. 38A and 38B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 39 shows various aberrations of the zoom lens system according to Example 10 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 40A and 40B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.150, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 10 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 11

FIG. 41 is a diagram showing a sectional view of a zoom lens system according to Example 11 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 41, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged between the positive meniscus lens and the second cemented lens in the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 11 of the third embodiment, vibration reduction coefficient K is 1.02, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.367 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.70, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.453 (mm).

Various values associated with Example 11 of the third embodiment of the present invention is listed in Table 11.

TABLE 11 [Specifications] f = 71.40 134.90 294.00 FNO =  4.10  4.28  5.79 2ω = 22.51°  11.74°  5.43° [Lens Data] r d ν n 1 494.1160 3.3593 64.14 1.516330 2 −494.1160 (d2) 3 74.6142 2.5000 26.52 1.761821 4 50.2492 8.5170 70.23 1.487490 5 −409.6962 (d5) 6 −572.2854 1.4000 49.60 1.772499 7 118.2999 1.5934 8 −150.1597 1.4000 49.60 1.772499 9 28.9590 4.2332 23.78 1.846660 10 159.4762 2.3641 11 −56.2166 1.4000 49.60 1.772499 12 737.8222 (d12) 13 255.4424 3.4925 51.47 1.733997 14 −65.2491 0.2000 15 55.4617 5.8677 81.54 1.496999 16 −42.2335 1.4000 34.97 1.800999 17 391.1593 0.2000 18 29.8308 4.2307 60.64 1.603112 19 109.3078 9.9568 20 ∞ 1.0000 Aperture Stop S 21 111.2314 1.3000 23.78 1.846660 22 34.2913 3.8688 70.23 1.487490 23 −116.1639 3.0066 24 131.0022 2.6204 25.42 1.805181 25 −42.8081 1.2000 39.58 1.804398 26 35.6448 6.4837 27 44.2831 3.9886 31.07 1.688931 28 −53.8284 2.7522 29 −23.7792 1.2000 49.60 1.772499 30 −254.9277 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40000 134.90024 294.00000 d2 16.22141 16.22141 16.22141 d5 2.00000 33.62022 46.49954 d12 29.66797 18.37991 2.00000 B.f. 47.57563 53.66382 85.74428 [Moving Amount upon Focusing] f 71.40000 134.90024 294.00000 δ1B 13.90148 14.20164 13.03481 [Values for Conditional Expressions] (16) f1/fw = 1.787 (17) f2/f2 = −0.436 (18) f3/fw = 0.500 (19) f32/f3 = −1.738 (20) f3/f33 = 0.063 (21) n31N − n31P = 0.304 (22) ν31P − ν31N = 46.57 (23) ν32N − ν32P = 14.16 (24) (r32R + r32F)/(r32R − r32F) = −1.748 (25) r32S/f32 = 0.690 (26) f1A/f1B = 2.860

FIGS. 42A and 42B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 43 shows various aberrations of the zoom lens system according to Example 11 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 44A and 44B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 11 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 12

FIG. 45 is a diagram showing a sectional view of a zoom lens system according to Example 12 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 45, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 12 of the third embodiment, vibration reduction coefficient K is 1.20, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.312 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.80, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.428 (mm).

Various values associated with Example 12 of the third embodiment of the present invention is listed in Table 12.

TABLE 12 [Specifications] f = 71.40 134.90 294.00 FNO =  4.11  4.34  5.80 2ω = 22.59°  11.77°  5.43° [Lens Data] r d ν n 1 470.2040 3.4304 64.14 1.516330 2 −470.2040 (d2) 3 66.8958 2.5000 26.52 1.761821 4 45.5528 9.0276 70.23 1.487490 5 −449.7939 (d5) 6 −402.2639 1.4000 49.60 1.772499 7 87.3056 1.8292 8 −109.2528 1.4000 49.60 1.772499 9 27.2177 4.2493 23.78 1.846660 10 238.8473 2.0018 11 −54.2941 1.4000 49.60 1.772499 12 405.9871 (d12) 13 ∞ 1.0000 Aperture Stop S 14 202.2803 3.3407 51.47 1.733997 15 −69.7514 0.2000 16 49.4756 6.2066 81.54 1.496999 17 −36.3641 1.4000 34.97 1.800999 18 417.1479 0.2000 19 30.2273 4.0221 60.64 1.603112 20 106.7084 4.7396 21 66.4249 1.3000 23.78 1.846660 22 38.1999 4.3369 70.23 1.487490 23 −91.4989 3.0000 24 195.2029 2.8722 25.42 1.805181 25 −40.8879 1.2000 39.58 1.804398 26 39.1832 12.6471 27 71.7192 2.3982 31.07 1.688931 28 −76.4137 1.3004 29 −21.7636 1.2000 49.60 1.772499 30 −61.3686 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distance] (Infinity) f 71.40008 134.89998 294.00000 d2 14.05307 14.05307 14.05307 d5 2.00000 33.03379 46.59044 d12 25.89044 16.74440 2.00000 B.f. 54.45490 59.34588 88.75509 [Moving Amount upon Focusing] f 71.40008 134.89998 294.00000 δ1B 11.82193 12.07969 12.36388 [Values for Conditional Expressions] (16) f1/f2 = 1.653 (17) f2/fw = −0.379 (18) f3/fw = 0.491 (19) f32/f3 = −1.762 (20) f3/f33 = −0.120 (21) n31N − n31P = 0.304 (22) ν31P − ν31N = 46.57 (23) ν32N − ν32P = 13.93 (24) (r32R + r32F)/(r32R − r32F) = −1.502 (25) r32S/f32 = 0.662 (26) f1A/f1B = 2.960

FIGS. 46A and 46B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 47 shows various aberrations of the zoom lens system according to Example 12 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 48A and 48B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 12 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 13

FIG. 49 is a diagram showing a sectional view of a zoom lens system according to Example 13 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 49, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged between the 32 lens group G32 and the 33 lens group G33, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 13 of the third embodiment, vibration reduction coefficient K is 1.22, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.306 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.77, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.435 (mm).

Various values associated with Example 13 of the third embodiment of the present invention is listed in Table 13.

TABLE 13 [Specifications] f = 71.40 134.90 294.00 FNO =  3.99  4.07  5.80 2ω = 22.60°  11.74°  5.43° [Lens Data] r d ν n 1 435.2356 3.5738 64.14 1.516330 2 −435.2356 (d2) 3 65.0718 2.5000 26.52 1.761821 4 44.2697 9.2741 70.23 1.487490 5 −463.1280 (d5) 6 −312.4330 1.4000 49.60 1.772499 7 89.0862 1.9706 8 −89.6775 1.4000 49.60 1.772499 9 27.3391 4.2567 23.78 1.846660 10 234.4984 1.8028 11 −63.7183 1.4000 49.60 1.772499 12 421.2241 (d12) 13 128.9757 3.6394 49.34 1.743198 14 −65.2871 0.2000 15 45.1211 6.2141 81.54 1.496999 16 −34.9173 1.4000 33.89 1.803840 17 179.4381 0.2000 18 28.1967 3.1441 61.13 1.589130 19 51.4191 3.2906 20 61.2265 1.3000 23.78 1.846660 21 41.2033 4.3881 70.23 1.487490 22 −71.4444 3.0000 23 2400.8873 2.8952 25.42 1.805181 24 −34.5253 1.2000 40.10 1.762001 25 43.6975 3.0000 26 ∞ 10.7331 Aperture Stop S 27 109.9589 2.6855 33.79 1.647689 28 −56.7968 1.6430 29 −21.1003 1.2000 50.23 1.719995 30 −54.1165 (B.f.) Wide-angle end Intermediate Telephoto end 8 Variable Distances] (Infinity) f 71.40000 134.90000 294.00000 d2 13.51363 13.51363 13.51363 d5 2.06047 33.56902 45.03690 d12 27.97643 18.33799 2.00000 B.f. 55.73858 57.28561 87.73867 [Moving Amount upon Focusing] f 71.40000 134.90000 294.00000 δ1B 11.13016 11.34131 11.58141 [Values for Conditional Expressions] (16) f1/fw = 1.600 (17) f2/fw = −0.382 (18) f3/fw = 0.512 (19) f32/f3 = −1.730 (20) f3/f33 = −0.099 (21) n31N − n31P = 0.307 (22) ν31P − ν31N = 47.65 (23) ν32N − ν32P = 14.68 (24) (r32R + r32F)/(r32R − r32F) = −1.037 (25) r32S/f32 = 0.546 (26) f1A/f1B = 2.791

FIGS. 50A and 50B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 51 shows various aberrations of the zoom lens system according to Example 13 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 52A and 52B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 13 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 14

FIG. 53 is a diagram showing a sectional view of a zoom lens system according to Example 14 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 53, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged between the 31 lens group G31 and the 32 lens group G32, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.20, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.312 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.75, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.440 (mm).

Various values associated with Example 14 of the third embodiment of the present invention is listed in Table 14.

TABLE 14 [Specifications] f = 71.40 134.91 294.00 FNO =  4.07  4.21  5.80 2ω = 22.52°  11.72°  5.42° [Lens Data] r d ν n 1 469.3093 3.4317 64.14 1.516330 2 −469.3093 (d2) 3 70.6717 2.5000 26.52 1.761821 4 47.9817 8.6474 70.23 1.487490 5 −513.7728 (d5) 6 −449.1622 1.4000 49.60 1.772499 7 121.4673 1.3256 8 −170.8246 1.4000 49.60 1.772499 9 25.7253 4.1467 23.78 1.846660 10 114.2679 2.1893 11 −58.0505 1.4000 49.60 1.772499 12 427.6062 (d12) 13 184.6338 3.0978 52.64 1.740999 14 −77.4294 0.2000 15 60.5320 6.2886 81.54 1.496999 16 −38.0057 1.4000 34.97 1.800999 17 −2769.6388 0.2000 18 29.4015 3.3326 60.64 1.603112 19 65.7395 7.2941 20 48.4532 1.3000 23.78 1.846660 21 28.7258 4.3311 70.23 1.487490 22 −116.3213 1.4000 23 ∞ 3.6000 Aperture Stop S 24 192.1240 2.6534 25.42 1.805181 25 −39.8609 1.2000 39.58 1.804398 26 36.5000 8.1971 27 74.0134 3.9109 31.07 1.688931 28 −49.3643 1.8413 29 −22.3167 1.2000 49.60 1.772499 30 −89.5841 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40015 134.90898 294.00094 d2 15.55650 15.55650 15.55650 d5 2.00494 36.17786 49.70524 d12 29.70030 19.40726 2.00000 B.f. 51.85087 54.13440 80.85104 [Moving Amount upon Focusing] f 71.40015 134.90898 294.00094 δ1B 13.28566 13.56940 13.82723 [Values for Conditional Expressions] (16) f1/fw = 1.743 (17) f2/fw = −0.414 (18) f3/fw = 0.506 (19) f32/f3 = −1.569 (20) f3/f33 = −0.048 (21) n31N − n31P = 0.304 (22) ν31P − ν32P = 46.57 (23) ν32N − ν32P = 14.16 (24) (r32R + r32F)/(r32R − r32F) = −1.469 (25) r32S/f32 = 0.703 (26) f1A/f1B = 2.756

FIGS. 54A and 54B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 55 shows various aberrations of the zoom lens system according to Example 14 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 56A and 56B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 14 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 15

FIG. 57 is a diagram showing a sectional view of a zoom lens system according to Example 15 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 57, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.16, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.322 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.75, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.440 (mm).

Various values associated with Example 15 of the third embodiment of the present invention is listed in Table 15.

TABLE 15 [Specifications] f = 71.40 134.90 294.00 FNO =  4.05  4.29  5.70 2ω = 22.57°  11.76°  5.44° [Lens Data] r d ν n 1 381.8649 3.2698 64.14 1.516330 2 −381.8649 (d2) 3 71.5714 2.5000 26.52 1.761821 4 49.9993 8.2004 81.54 1.496999 5 −1251.0960 (d5) 6 −459.6483 1.4000 49.60 1.772499 7 73.4579 2.3256 8 −148.2025 1.4000 49.60 1.772499 9 30.9506 4.0346 23.78 1.846660 10 507.9596 2.1322 11 −53.4502 1.4000 49.60 1.772499 12 745.1895 (d12) 13 ∞ 1.0000 Aperture Stop S 14 299.4180 2.5704 52.64 1.740999 15 −74.3861 0.2000 16 58.6516 5.0344 81.54 1.496999 17 −40.9400 1.4000 34.97 1.800999 18 −586.8839 0.2000 19 32.9311 3.0580 60.64 1.603112 20 86.6358 8.7020 21 66.7204 1.3000 23.78 1.846660 22 34.9761 4.3431 70.23 1.487490 23 −113.9382 5.0000 24 249.3959 3.6484 25.42 1.805181 25 −36.8058 1.2000 39.58 1.804398 26 39.1458 10.9499 27 57.2414 2.6768 31.07 1.688931 28 −326.2393 3.9442 29 −22.0804 1.2000 49.60 1.772499 30 −37.9653 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.40016 134.90320 294.00205 d2 14.63133 14.63133 14.63133 d5 2.00000 33.48260 46.17223 d12 28.49089 17.74860 0.31866 B.f. 48.78816 52.49212 81.78883 [Moving Amount upon Focusing] f 71.40016 134.90320 294.00205 δ1B 12.86620 13.12031 13.38598 [Values for Conditional Expressions] (16) f1/fw = 1.693 (17) f2/fw = −0.410 (18) f3/fw = 0.522 (19) f32/f3 = −1.566 (20) f3/f33 = 0.030 (21) n31N − n31P = 0.304 (22) ν31P − ν31N = 46.57 (23) ν32N − ν32P = 14.16 (24) (r32R + r32F)/(r32R − r32F) = −1.372 (25) r32S/f32 = 0.619 (26) f1A/f1B = 2.151

FIGS. 58A and 58B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 59 shows various aberrations of the zoom lens system according to Example 15 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 60A and 60B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.150°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 15 of the third embodiment shows superb optical performance correcting various aberrations.

EXAMPLE 16

FIG. 61 is a diagram showing a sectional view of a zoom lens system according to Example 16 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.

In FIG. 61, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.

The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.

The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.

The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a fixed stop S2, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.

An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).

Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.

Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.

In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.25, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.299 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.90, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.405 (mm).

Various values associated with Example 16 of the third embodiment of the present invention is listed in Table 16.

TABLE 16 [Specifications] f = 71.40 135.00 294.00 FNO =  4.05  4.29  5.70 2ω = 22.57°  11.76°  5.44° [Lens Data] r d ν n 1 340.6588 4.2 64.14 1.51633 2 −340.659 (d2) 3 65.1639 1.8 26.3 1.784696 4 45.8381 8.8 81.61 1.496999 5 −1308.92 (d5) 6 −271.25 1.4 49.61 1.772499 7 71.7854 1.3 8 −566.934 1.4 49.61 1.772499 9 24.4437 4.7 23.78 1.84666 10 133.0962 3.75 11 −46.0918 1.4 49.61 1.772499 12 1927.614 (d12) 13 ∞ 2 Aperture Stop S 14 188.6747 3.4 60.09 1.639999 15 −72.245 0.2 16 73.7218 6 81.61 1.496999 17 −38.1983 1.4 34.96 1.800999 18 −154.661 0.2 19 32.255 4.2 52.42 1.517417 20 143.854 7.9 21 333.5741 1.3 23.78 1.84666 22 54.3293 4.1 70.24 1.48749 23 −89.5707 10.2 24 256.9205 3.6 25.43 1.805181 25 −35.5686 1.2 39.59 1.804398 26 35.5686 3.4 27 ∞ 3.1 Fixed Stop S2 28 47.0802 4 34.47 1.639799 29 −96.8946 2.4 30 −23.3234 1.2 49.61 1.772499 31 −42.5579 (B.f.) Wide-angle end Intermediate Telephoto end [Variable Distances] (Infinity) f 71.39993 134.99982 294.00047 d2 13.43865 13.43865 13.43865 d5 2.49989 31.01849 43.01129 d12 28.21141 18.59271 2.50011 B.f. 53.40008 57.30852 87.10064 [Moving Amount upon Focusing] f 71.39991 134.99979 294.00046 δ1B 11.08175 11.28593 11.5251 [Values for Conditional Expression] (16) f1/fw = 1.563 (17) f2/fw = −0.368 (18) f3/fw = 0.525 (19) f32/f3 = −1.384 (20) f3/f33 = 0.238 (21) n31N − n31P = 0.304 (22) ν31P − ν31N = 46.57 (23) ν32N − ν32P = 14.16 (24) (r32R + r32F)/(r32R − r32F) = −1.321 (25) r32S/f32 = 0.685 (26) f1A/f1B = 2.051

FIGS. 62A and 62B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 63 shows various aberrations of the zoom lens system according to Example 16 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 64A and 64B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.

As is apparent from respective graphs, the zoom lens system according to Example 16 of the third embodiment shows superb optical performance correcting various aberrations.

In examples of the third embodiment, although three-group-type zoom lens systems have been proposed, it is needless to say that a zoom lens system merely adding a lens group to the three-group type zoom system is within the scope of the present invention. Moreover, in the construction of each lens group, it is needless to say that a zoom lens system merely adding a lens element to any one of lens groups of the zoom lens system according to the third embodiment is within the scope of the present invention.

Additional advantages and modification will readily occur to those skilled in the art. Therefore, the invention in its broader aspect is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

1. A zoom lens system comprising, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power, when a state of the zoom lens system varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increasing, and a distance between the second lens group and the third lens group decreasing, the first lens group being composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power, focusing from infinity to a close-range object being carried out by moving only the 1B lens group to the object, and the following conditional expressions being satisfied: 1.55<f1/fw<2.20 −0.55<f2/fw<−0.30 2.0<f1A/f1B<4.0 0.16<DAB/fw<0.30  where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused infinity.
 2. The zoom lens system according to claim 1, wherein when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group move to the object.
 3. The zoom lens system according to claim 2, further comprising a fourth lens group having negative refractive power to an image side of the third lens group, wherein when the state of lens group positions varies from the wide-angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group varies, and the following conditional expressions are satisfied: 0.35<f3/fw<0.70 −1.50<f4/fw<−0.70 −0.10<(D34w−D34t)/fw<0.10 where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34 w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34 t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.
 4. The zoom lens system according to claim 3, wherein the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions are satisfied: 50<ν1A 35<ν1BP−ν1BN where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.
 5. The zoom lens system according to claim 2, wherein the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions are satisfied: 50<ν1A 35<ν1BP−ν1BN where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.
 6. The zoom lens system according to claim 1, further comprising a fourth lens group having negative refractive power to an image side of the third lens group, wherein when the state of lens group positions varies from the wide-angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group varies, and the following conditional expressions are satisfied: 0.35<f3/fw<0.70 −1.50<f4/fw<−0.70 −0.10<(D34w−D34t)/fw<0.10 where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34 w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34 t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.
 7. The zoom lens system according to claim 6, wherein the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions are satisfied: 50<ν1A 35<ν1BP−ν1BN where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.
 8. The zoom lens system according to claim 1, wherein the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions are satisfied: 50<ν1A 35<ν1BP−ν1BN where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.
 9. The zoom lens system according to claim 8, wherein the negative meniscus lens and the positive lens in the 1B lens group are cemented with each other.
 10. A method for forming an image of an object and varying a focal length, comprising: providing a zoom lens system that includes, in order from the object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, the first lens group including, in order from the object, a 1A lens group having positive refractive power and a 1B lens group having positive refractive power; varying the focal length by increasing a distance between the first lens group and the second lens group, and decreasing a distance between the second lens group and the third lens group, when the state of the zoom lens system varies from a wide-angle end state to a telephoto end state; moving only the 1B lens group to the object to carry out focusing from infinity to a close-range object, wherein the following conditional expressions are satisfied: 1.55<f1/fw<2.20 −0.55<f2/fw<−0.30 2.0<f1A/f1B<4.0 0.16<DAB/fw<0.30  where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused on infinity.
 11. The method according to claim 10, wherein the first lens group and the third lens group are moved to the object, when the state of the zoom lens system varies from the wide-angle end state to the telephoto end state.
 12. The method according to claim 10, wherein the zoom lens system further includes a fourth lens group having negative refractive power to an image side of the third lens group, wherein when the state of the zoom lens system varies from the wide-angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group varies, and wherein the following conditional expressions are satisfied: 0.35<f3/fw<2.70 −1.50<f4/fw<−0.70 −0.10<(D34w−D34t)/fw<0.10  where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34 w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34 t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.
 13. The method according to claim 10, wherein the 1A lens group is composed only of one positive lens, and the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing the object and a positive lens having a convex surface facing the object, and wherein the following conditional expressions are satisfied: 50<ν1A 35<ν1BP−ν1BN  where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line. 